The invention relates to a ceramic decal for decoration with bright noble metal, comprising a backing sheet, a pattern or design layer made from a bright noble metal preparation, and a cover-coat on an acrylate resin basis.
Bright noble metal preparations, such as bright gold, bright platinum and bright palladium, for the decoration of glass, porcelain, ceramic and the like, consist of solutions of organic gold, platinum and palladium compounds, usually the sulforesinates, in organic media, which burn off completely or volatilize in the firing, and usually contain still other organic metal compounds, for example the resinates and sulforesinates of rhodium, bismuth and silver. The preparations are applied to the article to be decorated and fired on at temperatures between 500.degree. and 850.degree. C.
For the application of the decoration to the article, transfers or decals are customarily used, whose design layer consists of the bright noble metal preparation, or contains it, in addition to ceramic vitrifiable pigments, for example.
Such a decal is disclosed, for example, in German Pat. No. 1,232,168. It consists of a gummed paper as backing sheet, a design layer made from a bright noble metal preparation, a protective coating of an oxidizable or polymerizable material containing an alkyd resin, phenolic resin, urea resin or epoxy resin, or a drying or semidrying oil and a cover-coat on an acrylic resin basis.
The bright noble metal layers, which are only about 10.sup.-4 mm thick, are very sensitive to mechanical damage and chemical attack, for example by acids and alkaline detergents (dishwashing detergents), so that they are not very suitable for the decoration of rigorous day-to-day-used tableware.
To render the fired on bright noble metal layers resistant to wear and scratching and more stable chemically, they can be coated with a protective glaze in a very complex process that requires a second firing. Such a protective glaze can be obtained, as known for example from German Auslegeschrift No. 1,233,769, from borosilicate glaze frits dispersed in an oily medium or vehicle. In this process it is necessary first to fire the decoration and then, in a second firing, to fire on the protective glaze. This dual firing is required because the reaction of the organic vehicle contained in the glaze frit preparation with the bright noble metal preparations would otherwise degrade the brilliance and strength of adhesion of the bright noble metal layers.
The invention is addressed to the objectives of creating a ceramic decal comprising a backing sheet, a pattern or design layer made from a bright noble metal preparation, and a cover-coat on an acrylate resin basis, by which bright noble metal decorations protected by a transparent, colorless glaze layer on hard porcelain, soft porcelain, earthenware or enamel can be produced in a less expansive and cost-saving and energy-saving manner.